Active Margin Research Articles

Geochemical data, Nd and Hf isotopes and U–Pb geochronology of meta-mafic rocks from western Gondwana suture zone

The West Gondwana orogen, represented in NE Brazil by Santa Quitéria continental magmatic arc and ultrahigh-pressure metamafic rocks of a suture zone, have amphibolite and coesite-bearing retro-eclogite in both margins of the magmatic arc. This research reports and discuss the geochemical and geochronological data (U–Pb and Lu–Hf in zircon and Sm–Nd whole-rock) of amphibolite and retro-eclogite from the eastern margin of a continental magmatic arc. The Santa Quitéria Complex and metasedimentary Ceará Complex hosted these rocks. The Santa Quitéria amphibolites shows evident fractionation of REE. Nb–Ta–Ce anomalies evidence magma generated in a subduction zone with contribution and recycling of crustal sedimentary material, corroborate for slightly negative εNd (−1.56) and Paleoproterozoic NdTDM value (1.80 Ga). Isotopic Lu–Hf in zircon data indicates positive εHf (+5.00 to +7.78) and Neoproterozoic model ages (HfTDM from 0.97 to 0.86 Ga) (t = 637 ± 34 Ma - sample TJF5-258) indicate their extraction from the mantle. For the amphibolite samples from the Ceará Complex, the elemental distribution suggest that these rocks place them among oceanic basalts of enriched segments of mid-ocean ridges (E-MORB) and oceanic island basalts (OIB) – intra-oceanic arc basalts (IOAB). U–Pb zircon data of Ceará Complex amphibolite points to crystallization at ca. 670 Ma (674 ± 9 Ma, sample TJJV-07) and two metamorphic events around 640 Ma (644 ± 9 Ma) and 600 Ma (591 ± 5 Ma) related to the continental collision. Positive εNd values (+1.66 to +4.16) and model ages (NdTDM from 1.26 to 1.00 Ga) suggest a protolith crystallized from juvenile material of mantle source. Our data support that the eastern edge of the Santa Quitéria magmatic arc constitutes an active margin with subduction of the Cryogenian oceanic crust.

Drainage and sedimentary response of the Northern Andes and the Pebas system to Miocene strike‐slip tectonics: A source to sink study of the Magdalena Basin

AbstractMiocene strike‐slip tectonics was responsible for creating and closing short‐lived (ca. 6 Ma) passages and the emergence of isolated topography in the Northern Andes. These geological events likely influenced the migration and/or isolation of biological populations. To better understand the paleogeography of the Miocene hinterland and foreland regions in the Northern Andes, we conducted a source‐to‐sink approach in the Magdalena Basin. This basin is located between the Central and Eastern Cordilleras of Colombia and contains an ample Miocene record, which includes Lower Miocene fine‐grained strata and Middle Miocene to Pliocene coarsening‐up strata. Our study presents a new data set that includes detrital U–Pb zircon ages (15 samples), sandstone petrography (45 samples) and low‐temperature thermochronology from the Southern Central Cordillera (19 dates); which together with previously published data were used to construct a paleogeographical model of the Miocene hinterland and foreland regions in the Northern Andes. The evolution of the Magdalena Basin during the Miocene was characterized by playa and permanent lake systems at ca. 17.5 Ma, which may be related to a marine incursion into NW South America and western Amazonia. The appearance of Eocene to Miocene volcanic sources in the Honda Group after ca. 16 Ma suggests the development of fluvial passages, which connected the Pacific with the western Amazonia and Caribbean regions. These passages were synchronous with a time of Miocene exhumation and topographic growth (ca. 16 to 10 Ma) in the Central Cordillera and the transition from lacustrine to fluvial deposition in the Magdalena Basin. Middle to Late Miocene strike‐slip deformation promoted by oblique plate convergence and the oblique collision of the Panamá‐Chocó Block likely explains the synchronous along‐strike fragmentation and exhumation in the Central Cordillera.

Cumulate rocks of the Dumak ophiolitic mélange, Eastern Iranian Ranges: Composition, origin and tectonic implications

The Eastern Iranian Ranges are considered to be either a suture zone produced by closure of a Neo-Tethyan back-arc basin between the Lut and Afghan blocks or an oroclinal buckling of multiple terranes accreted to the active margin of the Neo-Tethyan Ocean. Both models are based on the presence of Cretaceous ophiolite complexes and sequences of Eocene turbiditic sedimentary rocks. The Dumak ophiolitic mélange, a significant ophiolitic assemblage that crops out in the western portion of the orogen adjacent to Lut, contains all the essential elements of a typical ophiolite in a matrix of serpentinite and clay-rich sediments. Ultramafic-mafic cumulates in the mélange are characterized by medium, non-rhythmic bedding in limited outcrops where they are in tectonic contact with other ophiolitic units. The cumulates consist of plagioclase-bearing dunite, troctolite, Cpx-troctolite and gabbro composed chiefly of olivine, plagioclase, and clinopyroxene accompanied by rare orthopyroxene. This assemblage is very similar to the differential crystallization sequence of tholeiitic magma at modern mid-ocean ridges. The clinopyroxene in these rocks is diopside (En = 47–49) and the plagioclase is bytownite (An = 71–77). Whole-rock geochemistry of samples from the crustal sequence of Dumak mélange are characterized by low TiO2 (0.03–0.17 wt%). Investigation of this crystalline sequence and geochemical properties of the rocks suggests that they can be considered as the low-Ti ophiolite originated from mid-ocean ridges. Additionally, the positive Eu anomalies as well as comparison of frequency of LREE and HREE in the mafic and ultramafic samples indicate the cumulates formed by fractional crystallization and differentiation of mantle-derived magmas. According to petrographic, geochemical, and structural evidence, it is possible that the Dumak ophiolite, after being formed or displaced between Lut and Afghan blocks, was firstly accreted to the south of the Lut block and then re-mixed into Eocene sediments emplaced in the current position.

Modeling Seismic Anisotropy Beneath the Island of Hispaniola via the Harmonic Decomposition of Receiver Functions

AbstractThe Caribbean Island of Hispaniola resulted from plate convergence that brought together distinct terranes and may include one or more active microplates. These processes may have brought seismically anisotropic materials to the island or created anisotropic structures through deformation. Our goal is to identify and model interfaces that bound seismically anisotropic media and/or dipping interfaces between isotropic layers beneath Hispaniola and assess the implications of our results for the region's tectonics. We perform harmonic decomposition of receiver function gathers for 17 broadband seismic stations deployed on the island. Our results reveal (a) a layer bounded by interfaces that produce opposite polarity on the transverse receiver functions at 25 and 41 km depth in the northern and eastern Dominican Republic that corresponds to the subducting North American oceanic lithosphere, (b) a layer at ∼8–17 km depth (also bounded by interfaces that produce opposite polarity) beneath the Cordillera Central in the central and eastern parts of the island that may indicate the crystalline, well‐differentiated lower crust of this long‐lived terrane, and (c) an interface that bounds anisotropic material at 22 km depth beneath southwestern Hispaniola. This last interface may correspond to the underthrusting Caribbean Large Igneous Province (CLIP), in which case it would mark the CLIP's upper boundary and the lower boundary is too gradual a transition to produce conversions.

Relationship Between Crustal Structure and Plate Convergence Around the Izu Collision Zone in Central Japan

AbstractWe conducted a receiver function (RF) analysis to understand the convergence process in and around the Izu collision zone. We calculated the P‐ and S‐wave RFs and converted them to depth using a three‐dimensional (3D) regional tomography model and regionally estimated near‐surface structure. We detected the Moho of the Philippine Sea Plate and determined its 3D geometry in and around the collision zone. In addition, we considered the 3D seismic velocity model, which was previously determined using seismic tomography, and we complemented a part of the Moho that we did not detect using the RFs. Based on the geometry of the upper surface of the Philippine Sea Plate determined in previous studies, the crust is >35 km thick beneath the Izu Peninsula and collision zone and becomes thinner (<20 km) moving east of the collision zone. Thus, the thick crust along the Izu‐Bonin arc collides, and the thin forearc crust subducts. A stable slip surface was previously assumed to exist at a 15–20 km depth beneath the Izu Peninsula and the collision zone. This study indicates that the surface should exist within the crust of the Philippine Sea Plate.

Description of the 1907 Aceh tsunami: impact (height, inundation and the travel time) on Cities of Banda Aceh, Meulaboh and Gunung Sitoli, Indonesia

There was tsunami in Aceh in 2004 with the height reached to 30 meter. It was caused by a 9.2 magnitude earthquake on the Sunda megathrust. The tsunami destroyed most of the buildings in affected cities and claimed many fatalities. However, there were many tsunami incidents around Aceh before 2004. Aceh is located in the northern Sumatera Island of Indonesia. It is part of the Great Sunda Arc subduction zone, a convergent boundary between the Indo-Australian and Eurasian plates. Records of pre-instrumental tsunami in this region are scarce. Here we describe a tsunami in Aceh that happened in 1907. It was caused by a magnitude 7.6 earthquake on the Sunda megathrust, similar to the tsunami Aceh in 2004. Details of parameter information like the height, inundation, and the arrival times as the parameters after shaking was felt to some cities like Banda Aceh, Meulaboh and Gunung Sitoli are lacking and we want to calculate the these parameters to the cities although with the poor information. Based on the magnitude, the deformation and the possibilities of the parameter of the tsunami to the cities are calculated and modelled from Well and Coppersmith (1994) equation. After that we estimate the tsunami height, inundation and the travel time with Bayesian Markov Chain Monte Carlo and we get the result in the cities that the tsunami height is about 3 m, arrival times ranging from 20 second to 48 second and an inundation between 66 m to 127 m.

Regional-scale resistivity structure of the middle and lower crust and uppermost mantle beneath the southeastern Canadian Cordillera and insights into its causes

SUMMARYSubduction zones are recognized as an important class of plate boundaries and are the location of a number of important geological processes. They are also important because of the mineral and geothermal energy resources formed by plate convergence. While subduction zones around the world have a number of common features, there are also significant differences among them. The Cascadia subduction zone in southern British Columbia is characterized by a relatively hot subducting plate, and a broad backarc region that is believed to exhibit a shallow, convecting asthenosphere. The magnetotelluric (MT) method is a useful tool to study subduction zones and backarc regions because measurements of subsurface resistivity are sensitive to the presence of fluids. A number of previous MT studies have taken place in this region, but they were limited to a 2-D approach to data analysis. As the MT method has developed, it has become clear that there is a significant advantage to using a 3-D approach to data analysis. This paper presents the first regional-scale 3-D resistivity model of the southern Canadian Cordillera and provides new insights into the lithospheric structure and the distribution of fluids. The southeastern Canadian Cordillera has high heat flow and numerous thermal springs, the locations of which are often controlled by faults. However, the deeper thermal structure and origin of the fluids are poorly understood. To develop an improved understanding of the structure of this area, MT data measured at 331 locations were used to create a 3-D model of subsurface electrical resistivity. This study is primarily focused on the Omineca and Foreland morphogeological belts in southeastern British Columbia, which are separated by the southern Rocky Mountain Trench. The resistivity model is presented to a depth of 100 km and a number of conductive features are observed in the crust and uppermost mantle of the southeastern Cordillera. The locations of these conductors broadly matched previously reported conductors, but the 3-D inversion revealed new details of their geometry. The previously reported Canadian Cordilleran Regional conductor was modelled as a number of discrete conductors in the depth range 15–55 km beneath the Omineca belt. Temperatures approximately in the range 400–700 °C are expected at depths of 15–26 km and saline aqueous fluids are likely the cause of the low resistivity. Temperatures approximately in the range 700–1300 °C are expected at depths of 26–55 km and small volumes of partial melt may explain the low resistivity. The Southern Alberta–British Columbia conductor, Red Deer conductor and Loverna conductor were imaged as a single connected conductor, whose low resistivity is likely caused by sulphide mineralization. A group of conductors was imaged near the southern Rocky Mountain Trench in the depth range 10–70 km and their low resistivity is likely caused by interconnected saline fluids and possibly interconnected graphite films. To understand if the distribution of thermal springs was correlated with the 3-D resistivity model, a statistical study was undertaken. This showed no clear correlation between crustal conductance and the distribution of thermal springs.

Deciphering influencing processes in a tropical delta system (middle-late Eocene? to Early Miocene, Colombian Caribbean): Signals from a well-core integrative sedimentological, ichnological, and micropaleontological analysis

Deltaic depositional systems are characterized by a complex interaction of physical, chemical, and biological factors. Although fluvial-, wave- and tidal-dominated deltaic environments have been extensively studied, evaluation of the processes in tropical mixed sedimentary systems has not been fully documented. Tropical regions with active margins are tectonic environments where these multiple factors act on the development of coastal systems. An onshore well-core from this tropical setting (Sinú-San Jacinto Basin, Colombian Caribbean) revealed that a middle-upper Eocene?-lower Oligocene coarse-grained deltaic setting is replaced by a thick coal-bearing mixed-energy fine-grained deltaic succession from the Oligocene to Early Miocene. The integrated analysis of facies associations, ichnological data, and terrestrial/marine micropaleontological assemblages (palynomorphs, foraminifera, and calcareous nannofossils) of this well-core allowed us to identify changes in dominance and influence of coastal processes (fluvial-, wave- and tide) and shoreline evolution. Using this information, as well as the sediment supply and accommodation space ratio, we were able to distinguish three intervals from the bottom to the top of the siliciclastic succession: (i) middle-late Eocene?–early Oligocene, prograding, fluvial-dominated, wave- and tide-influenced coarse-grained deltas with amalgamation of hyperpycnal-dominated mouth bars with hyperconcentrated flow input, (ii) Oligocene, retrograding to prograding, hyperpycnal-dominated heterolithic delta deposits punctuated by transgressive pulses, and (iii) late Oligocene to Early Miocene, aggradational, coal-bearing fine-grained delta plain with a higher proportion of transgressive phases over the continental environment. The complete succession represents long-term (∼14 Myr) mixed-energy nearshore siliciclastic systems, showing different lithological arrangements and sedimentation styles. A long-term evolution is observed from a middle-late Eocene? steep, short and coarse-grained sedimentary system with tropical humid lowland forest and punctual development of macrobenthic tracemaker communities (Interval I) to an Early Miocene gently (poorly drained), well-developed delta plain with mangroves and wave- and storm-influence record through trace fossils assemblages (Interval III). A combination of factors, including subsidence, relief uplifting, and possible relative sea level changes, are interpreted as the main controls on the stratigraphic evolution of sedimentary styles throughout the entire succession. Minor-order sedimentary successions into each interval (e.g., prograding distributary mouth-bar channel) revealed short-term cycles presumably controlled by an internal delta dynamic. Multidisciplinary analysis is essential for recognizing the influence of fluvial, wave, and tidal processes on tropical deltas, where high spatial and temporal variability makes it difficult to determine dominant processes for long periods of time.

Plate convergence controls long-term full-depth circulation of the South China Sea

How plate tectonics may affect full-depth ocean/sea circulation is not well understood. We used seismic data plus drilling/core and geomorphologic data to examine the influence of regional tectonics on South China Sea circulation. The features of four contourite depositional complexes across the sea, continental shelf to abyssal plain, indicate that plate convergence has controlled circulation within this marginal sea since the beginning of its closure, primarily via Luzon Strait changes. Initially (late Miocene), South China Sea circulation was open, as a part of North Pacific ocean circulation. Later (Pliocene to early Pleistocene) creation of the Luzon Strait reversed the direction of South China Sea surface circulation but not its deeper circulation. Subsequent (middle Pleistocene to present) narrowing and shallowing of the strait weakened surface, intermediate, and bottom flows within the sea but strengthened deepwater flow. This contourite-based approach to elucidating tectonic effects on surface-to-bottom paleo-circulation can be applied to other marine basins within an active tectonic setting.

Astrobiochronological calibration of an early Oligocene succession from the Colombian Caribe: Tectonostratigraphic implications

The Colombian Caribbean is an active margin characterized by constant and intense tectonic activity since the Cretaceous. Nonetheless, recent studies have reported a period of relative stability during the early Oligocene for some Caribbean basins. We have studied the biostratigraphic and well-log record of a 143-m sedimentary succession from the ANH San Jacinto-1 well in the Sinú-San Jacinto Basin. We present the first astrobiochronological age model constructed for the early Oligocene (32-28 Ma) based on the integrated use of planktonic foraminifer biostratigraphy and the gamma-ray record (GR). Rhythmic GR alternations, associated with changes in clay/organic matter concentration, exhibit a regular pattern of 1:2:5:20 and are correlated in amplitude and intensity with orbital cycles, being the eccentricity-related alternations, the most prominent signal imprinted in the GR record. The correlation with the astronomical target curves allowed us to establish a robust age model for the early Oligocene, which will be instrumental for defining future high-resolution correlations in the Colombian Caribbean basins. Orbitally driven GR patterns indicate that changes in sediment yield are associated with seasonal climatic changes, revealing that during eccentricity maxima (likely precession minima), enhanced humid climate conditions existed in the Caribbean area. At the same time, reduced precipitations persisted over eccentricity minima (likely precession maxima). The GR record amplitude also suggests that at times of reduced precession-driven Equatorial insolation, the obliquity exerted a larger control over the clay-rich sediment input, likely via enhanced humid conditions.

Ghost-arc geochemical anomaly at a spreading ridge caused by supersized flat subduction

The Southern Atlantic-Southwest Indian ridges (SASWIR) host mid-ocean ridge basalts with a residual subduction-related geochemical fingerprint (i.e., a ghost-arc signature) of unclear origin. Here, we show through an analysis of plate kinematic reconstructions and seismic tomography models that the SASWIR subduction-modified mantle source formed in the Jurassic close to the Georgia Islands slab (GI) and remained near-stationary in the mantle reference frame. In this analysis, the GI lies far inboard the Jurassic Patagonian-Antarctic Peninsula active margin. This was formerly attributed to a large-scale flat subduction event in the Late Triassic-Early Jurassic. We propose that during this flat slab stage, the subduction-modified mantle areas beneath the Mesozoic active margin and surrounding sutures zones may have been bulldozed inland by >2280 km. After the demise of the flat slab, this mantle anomaly remained near-stationary and was sampled by the Karoo mantle plume 183 Million years (Myr) ago and again since 55 Myr ago by the SASWIR. We refer to this process as asthenospheric anomaly telescoping. This study provides a hitherto unrecognized geodynamic effect of flat subduction, the viability of which we support through numerical modeling.

Seismicity pattern of African regions from 1964–2022: b-value and energy mapping approach

The African continent is one of the few tectonic plates where very few earthquakes have been reported. Sporadic poor data have jeopardized efforts to assess seismic hazards. In light of the tectonic setting, a review of the continent’s seismicity is crucial for predicting seismic hazards. For this study, seismicity data from USGS and ISC catalogs were collected from 1964–2022, in the latitude range of 40oS-40oN and longitude 20oW-52oE, from the surface to 700 km deep. Gutenberg’s parameters as well as the spatial variation of seismic energy were then analyzed as an assessment of Africa’s seismicity. The results show that NE Africa is at a higher stress level in terms of energy release than NW Africa. The Richter and Guttenberg’s constants of a = 5.61, b = 0.59; a = 6.55, b = 0.77; a = 6.44, b = 0.78; a = 7.41, b = 0.92; a = 5.94, b = 0.86; a = 5.97, b = 0.77 with the corresponding magnitude of completeness, mc, observed to be 3.7, 4.1, 4.4, 4.7, 4.8 and 4.6 were found for regions NW, NE, southern, eastern, western and central Africa, respectively. The distribution of focal depths vs. magnitude revealed that most of the seismicity is inherently shallow in its nature with an average focal depth of 21.22 km. In comparison, NW experiences relatively more profound events with an average depth of 32.19 km. A substantial rise in focal depth in North Africa is associated with the collision boundary. This information as a constraint on the tectonic plate near convergent boundary could be useful in plate modeling. Key Policy Highlights The higher stress observed in the North Africa and East Africa continent is vital for policy makers for sustainable built environment The estimated minimum magnitude cut-off Mw 3.7 reveals that the recording facilities in African continent is now improving. An increased focal depth distribution of events in North Africa infers there is plate convergence and can be used to constrain African tectonic plate for plate modeling.

A Discussion on the relationship between prominent unconformities on the SCS shelf margins and the end of seafloor spreading in the South China Sea

In an effort to reconcile different data sources (seafloor spreading, seismic and gravity images, well calibrations, outcrop studies) in the South China Sea (SCS), we reviewed the unconformity records, in particular in the context with the shut-off of seafloor spreading in the SCS. With respect to the start of spreading, there is a consensus: ca. 34-41 Ma. Recent data infer an end of spreading, near to the magnetic Anomaly 5 = ca. 15.5 Ma (Langhian age). In Northwest Borneo, it is suggested that this event is coeval with the Deep Regional Unconformity (DRU) in Sabah and Brunei, and the Mid-Miocene Unconformity (MMU) in Sarawak. The MMU is also recognized in offshore Vietnam and Palawan, on the Western and Southeastern margins of the SCS, respectively. The MMU/DRU may constitute the border between active margin and passive margin deposits within the marine SCS sub-basins. The progradation of clastic shelves post-MMU/DRU may have hampered growth of bioherms whilst creating prolific sandstone reservoir sequences offshore Northwest Borneo and Vietnam.

Geological controls on the distribution of gas hydrates in the shallow parts of the gas hydrate stability zone – constraints from seafloor drilling off Taiwan

The presence of gas hydrates is well known in the marine realm southwest of Taiwan due to the widespread distribution of bottom simulating reflectors in seismic records. To learn more about gas hydrate systems and their dynamics at passive and active margins, we drilled boreholes with MARUM-MeBo200 seafloor drill rig at areas where geophysical indications for gas hydrates have been detected in the past. Several gas hydrate proxies like negative chloride anomalies in the pore water, cold spots detected by infrared thermal scans on cores, increased resistivity, and lithological parameters clearly showed the presence of hydrates in the drilled sections. However, gas hydrate was not recovered by MeBo most likely because of small crystal sizes which dissociated during recovery from the seafloor. Three holes were drilled at southern summit of Formosa Ridge down to 126 m below seafloor (mbsf) and recovered sediments from which in situ hydrate saturation values were estimated between 1 and 10% at 15–42 mbsf and even higher values of up to 38% below 100 mbsf. The latter are probably related to the sealing effect of carbonate precipitation which occur at 85–95 mbsf directly above the hydrate-enriched layer. Four holes were drilled at Four-Way Closure Ridge where a maximum drilling depth of 143.90 mbsf was reached. Hydrate presence starts in 65 mbsf continuing down-core with a range of 1–29% gas hydrate saturation in fine-grained homogenous clay. An abrupt change to higher gas hydrate saturation values of up to 80% occurs below 109 mbsf where silty and sandy turbidite layers are often intercalated. Such high gas hydrate contents only occur in the sand layers and not in the fine-grained sediments intercalated to the sand deposits.

Abstract 6770: Spatial characterization of immune microenvironment from early onset metastatic colorectal cancer (EOmCRC) showed a dual prognostic role for IDO1 expression

Abstract Background: Epidemiological studies demonstrate that the incidence of CRC in young adults is continually rising in both Europe and the USA. The differences between the spatial distribution of immune related markers (IRM) and their prognostic role in EOmCRC compared to late onset (LOmCRC) remains to be elucidated. Methods: Forty paraffin embedded formalin fixed unstained sections from patients (pts) diagnosed with either EOmCRC (≤45) or (≥50) LOmCRC, matched for chemotherapy (chx) and molecular features, all with microsatellite stable disease were included. All tissue samples were obtained from pts enrolled in SPECTAcolor (EORTC-40CRC-GITCG) platform trial. The expression of IRM was studied using the GeoMX Digital Spatial Profiler (DSP). Fifty-seven IRMs were used and three morphology markers (MMs) anti-CD45, pan-cytokeratin and SYTO 13. Three 300 μm regions of interest (ROIs) were selected within the core of the tumour and further 3 ROIs within the active margin of the tumour. Each ROI was segmented based on MMs to obtain a tumour microenvironment (TME) and a tumour (T) mask. The analysis used the GeoMX DSP Advanced Analysis Suite software, R and IBM SPSS. Control for multiple comparisons use a false discovery rate (FDR) threshold of 0.05. Results: Samples from 40 pts were collected; 19 (47.5%) were EOmCRCs; 16 (40%) were female; 23 (57.5%) with pathological stage IV. The majority being, 23 (57.5%) grade ≥ 2, left sided 26 (65%), oxaliplatin based first line chx 23 (57.5%). Ten (25%) were KRAS mutant (mt), 1 (2.5%) NRAS mt and 1 (2.5%) BRAF mt. The median overall (OS) and progression free survival (PFS) for the entire cohort was 36.6 months (m) 95%CI (33.5 - 39.7) and 11.7 m (8.1 - 15.3), respectively.The <0.05 FDR differential expression analysis based on tissue segmentation uncovered 9 hits when comparing the TME between different age groups and 2 hits when comparing T segments, all overexpressed in LOmCRC. Indoleamine 2,3-dioxygenase 1 (IDO1) was differentially overexpressed in TME (adjusted p=0.043) and T (adjusted p=0.042) for LOmCRC.In the EOmCRC group IDO1 relative high expression in T was an independent marker associated with worse survival outcomes after multivariate cox regression corrected for the rest of significant markers (MVCC) for OS, HR: 7.01*105 95%CI (9.08*105-5.41*1010), p=0.003 and PFS, HR:7.7*105 95%CI (1.96-30.3*106), p=0.029. However, interestingly high IDO1 in TME was an independent marker associated with better OS, HR: 0.02 95%CI (0.01-0.46), p=0.015. Conclusion: Differential expression analysis of IRMs found IDO1 as differentially expressed in both segments (T and TME). Furthermore, high IDO1 expression seemed to have a dual prognostic role depending on the segment analysed, showing worse OS when found in the tumour but better OS when found in tumour microenvironment for early onset mCRC. Citation Format: Raghavendar Thyagaraja Nagaraju, Jakub Franczak, Markus Möhler, Elisa Fontana, Anne Giraut, Lieve Dirix, Jose Casas-Martin, Beatrice Borelli, Florian Lordick, Elizabeth Smith, Sabine Tejpar, Gunnar Folprecht, Jorge Barriuso. Spatial characterization of immune microenvironment from early onset metastatic colorectal cancer (EOmCRC) showed a dual prognostic role for IDO1 expression. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6770.

The State-Dependent Effectiveness of Hiring Subsidies

The responsiveness of job creation to shocks is procyclical, while the responsiveness of job destruction is countercyclical. This new finding can be explained by a heterogeneous-firm model in which hiring costs lead to lumpy employment adjustment. The model predicts that policies that aim to stimulate employment by encouraging job creation, such as hiring subsidies, are significantly less effective in recessions: these are times when few firms are near their hiring thresholds and many firms are near their firing thresholds. Policies that target the job destruction margin, such as employment protection subsidies, are particularly effective at such times. (JEL E24, E32, H25, J23, J64)

Geochemical and radiometric data for mafic rocks from the Guleman Ophiolite (SE, Turkey): New insights on the geodynamic evolution of the southern Neo-Tethyan ocean

The Guleman Ophiolite is located in the southeast of Turkey and mainly consists of harzburgites and dunites hosting economically viable chromitite bodies, and lesser amounts of cumulate and isotropic gabbro, diabase dykes, pyroxenite and locally plagiogranite. This study reports the combined whole-rock geochemical and radiogenic isotope (Sr and Nd) data for gabbro and diabase dykes, and in-situ zircon U-Pb geochronological data for plagiogranite and gabbro from the Guleman Ophiolite. Two different geochemical groups were determined based on immobile minor and trace elements, and radiogenic isotope characteristics of gabbro and diabase dykes investigated here. The first group is represented by boninites and displays highly depleted elemental patterns compared to NMORB, and spoon-shaped rare earth element profiles. Contrarily, the second group resembles back-arc basin basalts and is characterized by NMORB-like rare earth element patterns associated with negative Nb anomalies. The boninitic samples are characterized by less radiogenic 143Nd/144Nd(i) (0.51229 to 0.51267; ƐNd = −4.8 to +2.7) and more radiogenic 87Sr/86Sr(i) (0.70549 to 0.70758) isotope compositions compared to the back-arc basin basalt-like samples (143Nd/144Nd(i) = 0.51289 to 0.51296; ƐNd = +7.0 to +8.4; 87Sr/86Sr(i) = 0.70496 to 0.70629), indicating derivation from distinct and/or heterogeneous mantle source regions within a supra-subduction zone. The LA–ICP–MS zircon U-Pb analyses yielded concordant late Cretaceous ages for gabbro (82 ± 2.9 Ma) and plagiogranite (79.9 ± 0.8 Ma) samples. The overall geochemical, isotopic and geochronological data presented here suggest that the Guleman Ophiolite consists of forearc and initial back-arc spreading sections of oceanic crust, which may have been formed in an intra-oceanic subduction zone within the Berit Ocean (northern branch of the southern Neo-Tethyan ocean). Moreover, the generation of continental arc magmatism (i.e. Baskil and Esence Granitoids) was well-documented on the active margin of the Malatya-Keban Metamorphics to the north. Therefore the closure of this oceanic basin should have resulted in multiple coeval northward subduction events during the late Cretaceous.

Flat subduction in the Early Earth: The key role of discrete eclogitization kinetics

Flat (shallow) subduction is mainly proposed as an Archean-Paleoproterozoic process, contributing to the growth of continental lithosphere. However, numerical models of Precambrian subduction commonly show steep subduction. Here we investigate the effects of lithology-dependent eclogitization (minor for gabbroic lower crust, strong for basaltic upper crust) of oceanic crust during subduction. We performed 2D petrological-thermomechanical modeling of subduction at potential mantle temperatures up to 250 °C warmer than present, using a numerical approach that accounts for buoyancy effects from both mantle depletion and eclogitization. The modeling reveals that increases in mantle potential temperature and the related thickness of oceanic crust and depleted mantle may induce transition to the flat subduction regime at ΔT ≥ 150 °C but only when a delayed eclogitization of gabbroic compared to basaltic crust is taken into account. Otherwise, subduction operates in the steep slab regime. Flat Precambrian subduction models show episodic bimodal magmatism within arcs located > 400 km from the trench, caused by short-lived (1–4 Myr) subduction transients consisting of three consecutive stages: (1) twisting downward of the eclogitized slab portion, (2) subvertical descent and break-off of this twisted portion, (3) rising of the remnant non-eclogitised slab tip and continuation of flat subduction. Limited formation of TTG-series granitoids is caused by partial melting of the subducting basaltic layer but becomes less pronounced at ΔT = 250 °C. Flat subduction produces an overthickened, layered keel-like continental mantle root, with an intermediate layer of subducted oceanic crust. However, construction of long-lived mantle keels by this mechanism might be limited by peeling off of the gradually eclogitizing oceanic crust and the underlaying mantle when plate convergence ends. At elevated mantle temperatures flat subduction produces voluminous hydration of the mantle wedge, forming a subcrustal serpentinite mélange layer that becomes a potential source of fluids in the subsequent evolution of the overlying continental crust.

Rapid active thrust faulting at the northern Alaska Range front

AbstractPlate convergence rates strongly influence seismicity and mountain building inboard of convergent margins, but the distribution and kinematics of structures accommodating farfield convergence can be elusive. In interior Alaska, Yakutat microplate convergence drives late Pleistocene–recent right slip on the Denali fault, but westward-decreasing slip rates leave substantial residual Yakutat motion unaccounted for. Here, we show that Northern Foothills thrust slip beneath the northern Alaska Range absorbs a modern 4.4 mm/yr geodetic velocity gradient equivalent to ~78% of the 5.6 mm/yr residual Yakutat convergence along the central Denali fault. Infrared-stimulated luminescence ages of strath terrace deposits (67–4 ka; six sites) quantify Totatlanika River bedrock incision across the 1947 Mw 7.1 thrust earthquake epicentral region. Incision rates increase abruptly from <1 mm/yr to 4.8–5.6 mm/yr above the blind thrust tip near the range front. Rapid slip at 6.7 mm/yr on a steep thrust ramp beneath the northern Alaska Range front accommodates the geodetic gradient, drives rock uplift at rates matching measured incision rates, and implies that large earthquakes like the 1947 event may recur with 500–1400 yr frequency. Results illuminate focused seismogenic strain inboard of a complex convergent margin and prompt reevaluation of Alaska’s neotectonic framework.

Geochemical characteristics of the Middle–Late Permian sedimentary rocks in the southern Great Xing'an Range, NE China, and their constraints on the closure time of the Paleo Asian Ocean (Eastern Segment)

The Late Paleozoic sedimentary environment in the southern Great Xing'an Range in Northeast (NE) China, and the timing of the final closure of the Paleo Asian Ocean between the North China Craton and combined NE China blocks have been controversial for a long time, affecting and restricting the exploration and development of new area and new strata in the North Area in China. In order to reconstruct the structural-sedimentary evolution history of the southern Great Xing'an Range during the Middle to Late Permian, and to explore the closure time of the Paleo Asian Ocean (Eastern Segment), in this paper, the sedimentary characteristics and tectonic background of the Middle–Late Permian sedimentary rocks from well MKD1 are systematically analyzed by using elemental and organic geochemistry methods. The results show that the Middle Permian sedimentary records in well MKD1 show typical marine sediments, while the Late Permian sediments change significantly to clastic rocks deposited in the marine–continental transitional environment. The provenances of the Middle Permian rocks are mainly intermediate and felsic igneous rocks from continental active margin and oceanic island arc tectonic setting, related to the northern accretion complex, and the Songnen Block and partially arc magmatic rock. The source materials of the Late Permian rocks are mainly felsic rocks and some intermediate igneous rocks from the continental arc and active margin, related to the northern accretion complex, the arc magmatic rock and the Songnen Block. Depositional discontinuity after the Late Permian, regional lackness of the Early Triassic strata, sedimentary environment variation, tectonic setting and provenance location discrimination of the Middle–Late Permian rocks comprehensively reveal that the Paleo Asian Ocean (Eastern Segment) possibly closed in the late Late Permian. Finally, we propose a structural-sedimentary evolution pattern of the southern Great Xing'an Range during the Middle to Late Permian.